1. Field of the Invention
The present invention relates generally to an improved heat sink structure and a manufacturing method thereof, and more particularly to an annular heat sink structure and a manufacturing method thereof.
2. Description of the Related Art
The conventional cylindrical heat sink includes a cylindrical body and multiple radiating fins connected to the circumference of the cylindrical body. There are several conventional measures for connecting the radiating fins to the circumference of the cylindrical body. For example, Taiwanese Invention Patent Application No. 098105429 discloses a cylindrical heat sink and a method of tightly planting radiating fins of the heat sink and an application device thereof. According to the method, a mold seat drivable by a power source to create stepped rotational operation is provided. A cylindrical body is located on the mold seat. The circumference of the cylindrical body is formed with multiple channels. A radiating fin assembly is provided. The radiating fin assembly includes multiple radiating fins arranged on a lateral side of the mold seat. The cylindrical body intermittently rotates to drive and align the channels with the radiating fins. A radiating fin insertion device is used to push the radiating fins and sequentially insert and locate the radiating fins into the channels of the cylindrical body. After the radiating fins are fully inserted in the channels of the cylindrical body, a successive tightening process is performed to tightly integrally connect the radiating fins to the channels. Accordingly, the radiating fins are located on the circumference of the cylindrical body to form a heat sink.
One prior art discloses a tightening method for a heat sink. The heat sink includes a heat conduction base seat and a radiating fin assembly. One surface of the base seat is formed with multiple channels and guide grooves positioned between two channels. The radiating fin assembly includes multiple radiating fins. A mold having an internal space and a press end section is provided. A tightening/connection process is performed to press and insert the heat sink into the internal space of the mold. The press end section is axially thrust into the guide grooves to compress and deform the channels. At this time, the radiating fins are pressed to tightly integrally connect with the deformed channels. The above patent provides a heat sink pressing and riveting method better than the conventional heat sink manufacturing method. The breakage of the puncher or blade mold can be effectively reduced to promote the ratio of good products. Also, the precision and quality of the products are increased. This method is conveniently applicable to various heat sinks to form different types or shapes of heat sinks.
Another prior art discloses an improved assembly of heat sink radiating fins and base seat. The end of the radiating fin of the heat sink is formed with a folded root section with a predetermined shape. Multiple radiating fins are assembled into a radiating fin assembly by means of side latches or heat pipes. The connection face of the base seat is formed with insertion channels in adaptation to the radiating fins by means of an extrusion mold. The connection face of the base seat is further formed with elongated grooves. The insertion channels and the elongated grooves are alternately arranged.
The folded root sections of the radiating fins of the radiating fin assembly are simultaneously inserted into the insertion channels of the base seat. Then the elongated grooves are pressed to make the base seat very tightly riveted with the folded root sections of the radiating fins. By means of the design of the folded root sections, the contact area between the radiating fins and the base seat is greatly increased to effectively enhance heat transfer efficiency of the heat sink. Moreover, the insertion process is simple and time-saving and the radiating fins can be securely connected with the base seat by means of the insertion process. Furthermore, the assembling process can be completed without using electroplating, solder paste or any other media adhesive. This helps in maintaining the environment.
The other prior art discloses an improved heat sink with heat pipes. The heat sink includes a thermal module, a base seat and more than one heat pipe. The end of each radiating fin is formed with a folded root section. An upper end face of the base seat is formed with multiple insertion channels by means of an extrusion mold. The folded root sections of the radiating fins are inserted into the insertion channels of the base seat and tightly riveted with the base seat. More than one insertion groove is formed on a lower end face of the base seat. The heat pipe is correspondingly placed into the insertion groove and then pressed and flattened to tightly connect with the base seat by means of press fit. Accordingly, the bottom face of the heat pipe is formed with a flat section flush with the lower end face of the base seat. The flat section of the heat pipe attaches to and contacts with a heat-generating chip. Therefore, the heat can be directly transferred by the heat pipe and quickly dissipated.
In all the above patents, the radiating fin is first riveted with the channel and then the guide grooves on two sides of the channel are pressed to deform the channel and press the radiating fin to tightly integrally connect the radiating fin with the channel.
Such process has some problems as follows:                1. The riveting process is a pressing process in which a mechanical measure is used to connect two components into an integrated body. The radiating fin is connected with the channel by means of riveting so that the junction between the radiating fin and the channel is deformed. As a result, the junction between the radiating fin and the channel is irregular and gaps exist between the radiating fin and the channel. This will affect the heat transfer efficiency.        2. The outer surface of the cylindrical body not only is formed with the channels, but also is formed with the guide grooves. The channels and the guide grooves are alternately arranged. That is, the number of the channels per unit surface area is reduced. As a result, the number of the mounted radiating fins is reduced.        3. The guide grooves on two sides of the channel are pressed to deform the channel and press the radiating fin to tightly integrally connect the radiating fin with the channel. This is likely to make the edges of the opening of the channel outward curl and warp. Therefore, the opening of the channel will be expanded. As a result, the radiating fin is apt to detach from the channel.        4. The manufacturing method includes numerous steps so that the manufacturing time is quite long.        